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Melamine ‘widespread’ in China’s food chain

By Andy Coghlan and Reuters

Melamine, the chemical that has tainted milk formula in China and made thousands of children ill, may have been part of the food chain in China for a long time, say food experts. But the health effects of long-term exposure in adults are unclear.

So far, 53,000 infants have fallen ill after drinking formula milk deliberately adulterated with melamine. Four babies have died, 13,000 have been hospitalised and 104 are in a critical condition with kidney stones caused by the adulterant. A girl in Hong Kong has become the first case of poisoning outside China.

The makers of baby formula require their milk to have a high protein content, which they determine by measuring its nitrogen content. But farmers who produce milk that doesn’t meet this standard can beat the test by mixing it with melamine powder.

Common pollutant

The chemical (C3H6N6), a white, crystalline powder used to make plastics, fertilisers and cleaning products, has a high nitrogen content and so makes the milk appear high in protein.

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China’s inspection agency has identified 22 manufacturers selling contaminated baby milk. It has emerged that Sunlu, the formula milk supply company first implicated in Hebei province earlier this month, received complaints about sick babies as early as December last year. A documentary in July by Hunan TV reported an epidemic of kidney disease in the region.

However, milk isn’t the only way that melamine can enter the food chain. Chan King-ming, associate professor of biochemistry at the Chinese University, said cyromazine, a derivative of melamine, is very commonly used in China as a pesticide.

“It is absorbed into plants as melamine … of course, it is already in our food chain and animal feed,” says Chan. “So it is not just in milk products, but also in farm products and animal feed.” In principle, the chemical can enter the human food chain from any of these sources.

Unknown effects

But no studies have been carried out on the harm melamine can cause humans and experts are uncertain what effects it may have on people who may have been exposed to the chemical over the long term.

“What we know is that melamine gives kidney stones and problems in the kidney,” says Peter Yu, associate professor in applied biology and chemical technology at the Hong Kong Polytechnic University. “But we don’t know if there are other ill effects in the long term. These are ingredients that shouldn’t be in food,” he says.

Other experts say that, while kidney stones can be removed easily, melamine may cause other damage when it crystallises and blocks the small tubes in the kidney that filter blood.

Melamine first turned up last year in Chinese pet food exported to the US, where many cats and dogs developed acute kidney failure and died.

But in a report released in May 2007, the US Food and Drug Administration said its investigations found that consuming “pork, chicken, fish and eggs from animals that had inadvertently been fed animal feed contaminated with melamine … was very unlikely to pose a human health risk”.